Mechanism Of Water-saving Of Local Controlled Irrigation For Tomato In Greenhouse And Its Water Deficiency Diagnosis

China's greenhouse vegetable cultivation area of rapid development has played a huge rolein a balanced supply of vegetables anniversary. Facilities vegetable cultivation can not userainfall, the need for irrigation to ensure the production. Popular irrigation method ingreenhouse is still surface irrigation which causes serious waste of water. Controlled root zonealternate irrigation technology proposed systematically as local controlled irrigationtechniques, has become a research hotspot, which extends the traditional irrigation mode, timeand quantity controlled, and space controlled. In addition, the technology through crop partialroot in the relatively dry zone water deficit signal fed back can be achieved the physiologicalwater saving. Water deficit timely diagnosis is critical for the maintenance of the life health ofcrops. Research on the application of local controlled of irrigation in the greenhouse vegetablecultivation is still relatively few. So research on the water saving mechanism of localcontrolled irrigation for greenhouse vegetables and water deficit indicators to determine willimprove the irrigation scientific theory, and propose the basis of decision making for scientificirrigation, and has important scientific significance and application.The test of tomato irrigated was carried out during2002-2005in greenhouse and rainshelter at water-saving irrigation experiment station of Northwest A&F University. Thewater-saving mechanism, life healthy physical characteristics, soil environmental effects, soilmoisture dynamics and water consumption features, the diagnosis of tomato water deficitphysiological growth indicators and influencing factors of alternating local controlled dripirrigation for tomato were studied systematically. The main results are as following:(1) The study confirmed that the local controlled of irrigation can be properly controlledvigor, reduced height, to reduce the redundant growth of collateral, to grow the stem diameter,enhance tomato Vc content, sugar content and sugar acid ratio, the improvement of fruitnutrition and flavor. The alternate partial root zone drip irrigation of2/3irrigation amount ofconventional drip irrigation can increase root to shoot ratio, reduce redundant tomato growth,improve yield and water use efficiency, and realize saving30%or more. Alternate localrootzone drip irrigation in tomato root distribution of spatial characteristics, reveals local controlled irrigation can be modulated to form a good root conducive to tomato absorb waterand nutrients, and three-parameter exponential model simulation can be a good simulation ofroot spatial distribution of the root zone of ADI.(2) The physiological indices of tomato response to the local controlled irrigation, tomatoleaf photosynthetic rate and transpiration rate during the most of the time of the alternatepartial root zone drip irrigation is higher than its of conventional drip irrigation, buttranspiration increase slightly, so leaf water use efficiency increase. Local controlled irrigationto the dry side of the soil root signal can regulate stomata aperture, reducing transpiration,maintaining the balance of the tomato water absorption and water loss, especially themiddle-water amount treatments. ADI has a lower cell concentration and lower leaf waterpotential, and is good for maintaining the life and health characteristics of tomato.(3) Based on results of physiological and ecological monitoring system, fruit growth, stemdiameter, stem sap flow, leaf temperature changes of tomato under local controlled irrigationin different weather conditions and rules and influencing factors about the parametersmentioned above were systematic analyzed. It was found that: the diameter of the tomatofruit showing continuous fluctuations increasing trend; the growth rate during the day than atnight, sunny day is greater than a cloudy day; leaf transpiration rate is greater than theabsorbent capacity of the plant roots and stem diameter shrinkage in typical sunny day anddaytime were significantly larger than those in cloudy day and night time; leaf-airtemperature differences in sunny days were significantly greater than those in cloudy day;leaf temperature have significant relationships with air temperature, the total flux density andthe water vapor pressure deficit. The multiple linear regression models for leaf-airtemperature difference, air vapor pressure difference and total radiation flux density wasestablished and can successfully simulate changes of leaf temperatures. The values of relativesap flow under ADI tomato in sunny day were significant higher than that of DI, while thosein cloudy day under ADI and DI were not significant. The boundary line analysis was used toestablish the relationships between tomatoes stem sap flow and air temperature, air saturatedvapor pressure and total radiation flux density. It was found that the parameters mentionedabove showed significant correlation with relative stem sap flow. Multiple linear regressionequation for relative sap flow with the air vapor pressure deficit and the total radiation fluxdensity was established. The simulated results of relative sap flow by multiple linearregression equation were fitted well with the measured values.(4) Variations of local controlled irrigation on tomato leaf-air temperature difference, stemchanges, fruit diameter growth in the irrigation cycle were examined. It was found that therelationship between increment of fruit diameter and soil water content are not significant, and that cannot be used as the evaluation of soil containing water indicators; evaluation oftomato water deficit by the method of upper and lower baselines of Crop Water Stress Index(CWSI) were analyzed in this part. It was found that the afternoon values of CWSI cannot beused as indicators in the region of changeable weather, but that for the arid oasis region inNorthwest China has a certain degree of feasibility; MDS/ET0has a close relationship withsoil water content of irrigated compartment, and the influence of climate condition is small.MDS/ET0could be a stable indicator to guide irrigation.(5) Research the impact of local controlled of irrigation on soil water retentioncharacteristics, soil temperature and fertilizer use, soil water characteristic curve of the soil inlocal controlled irrigation of space micro-domain variation, assessment of the characteristicsof soil conservation and effective water found that local controlled irrigation to form a goodsoil structure; local controlled irrigation districts stratified soil temperature variation in growthperiod and soil temperature prediction model based on the temperature; measured pullseedlings after the tomato root zone layered micro-domain NPK residues, analysis of itsspatial distribution characteristics, and evaluation of fertilizer use.(6) whether it is vertical or horizontal root ADI, there is always a relatively dry region inthe tomato growing period, the local controlled irrigation to the formation of the waterenvironment of a water deficit signaling ABA; irrigation side of the soil moisture decreasedfaster rather than the irrigation side of the slow decline, the side of alternative irrigation is themain source of the tomato root water uptake; alternating vertical root zone drip waterconsumption was significantly lower than conventional drip irrigation of processing; theintensity of different root zone water is different, the overall upper greater than lower.The results show that the greenhouse vegetables using local controlled irrigation inconditions of medium irrigation amount for can increase output, water-saving andlife-sustaining health, and help form a good soil structure, and suitable soil temperature andefficient fertilizer use. Initially proposed based on stem diameter variation and CWSI waterdeficiency diagnosis method can provide guidance for irrigation precise controlled.